Scientists developed the first molecular-level comparison of photochemical effects on surrogate and Macondo (MC252) oil to better understand this weathering process and the toxicity mechanisms it produces.

Many researchers studying the effects of the Deepwater Horizon spill use surrogate oil in experiments because of limited availability of MC252. Even with similar geochemical properties, there are slight compositional differences in oils that can influence their response to photochemical degradation. Recent advances in analytical techniques now allow scientists to see more clearly the structural transformations in petroleum residues.

This study’s team exposed surrogate and MC252 oil to natural sunlight as water-soluble oil fractions formed (known as Water Accommodated Fractions or WAFs) in sterile seawater. Using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS), they measured WAFs in oil incubated in unfiltered full sunlight, sunlight with ultraviolet radiation blocked, and darkness.

“This study focuses on several critical issues related to oil spill research and provides insight into the effects of photo-toxicity,” said study authors Pamela Vaughan and Wade Jeffrey. They explained that their results raise the issue of a standard method for creating WAFs which is typically done under dark conditions, “Our data indicate that WAFs created under more natural conditions have a very different biological effect.” They continued, “Perhaps more importantly it highlights the effects of light exposure and resulting bacterial toxicity. Sunlight greatly increases the toxicity of oil to marine bacteria, but those photochemical changes in toxicity are driven by visible light, not the suspected ultraviolet radiation.”

The GoMRI is a 10-year independent research program established to study the effect, and the potential associated impact, of hydrocarbon releases on the environment and public health, as well as to develop improved spill mitigation, oil detection, characterization and remediation technologies. An independent and academic 20-member Research Board makes the funding and research direction decisions to ensure the intellectual quality, effectiveness and academic independence of the GoMRI research. All research data, findings and publications will be made publicly available. The program was established through a $500 million financial commitment from BP. For more information, visit http://gulfresearchinitiative.org/.